Lethal and sublethal effects of the pyrethroid, bifenthrin, on grass shrimp (Palaemonetes pugio) and sheepshead minnow (Cyprinodon variegatus)

This study investigated the lethal and sublethal effects of the pyrethroid insecticide bifenthrin on adult and larval grass shrimp, Palaemonetes pugio, and adult sheepshead minnows, Cyprinodon variegatus. The effects were determined by conducting 96-h aqueous static renewal tests and 24-h static tests with sediment. Oxidative stress biomarkers, lipid peroxidation, glutathione, and catalase were also assessed. The 96-h aqueous LC50 value for adult shrimp was 0.020 microg/L (95% CI: 0.015-0.025 microg/L) and for larval shrimp was 0.013 microg/L (95% CI: 0.011-0.016 microg/L). The 96-h aqueous LC50 for adult sheepshead minnow was 19.806 microg/L (95% CI: 11.886-47.250 microg/L). The 24-h sediment LC50 for adult shrimp was 0.339 microg/L (95% CI: 0.291-0.381 microg/L) and for larval shrimp was 0.210 microg/L (95% CI: 0.096-0.393 microg/L). The oxidative stress assays showed some increasing trends toward physiological stress with increased bifenthrin concentrations but they were largely inconclusive. Given the sensitivity of grass shrimp to this compound in laboratory bioassays, additional work will be needed to determine if these exposure levels are environmentally relevant.     

Quantification of bioavailable nickel in sediments and toxic thresholds to Hyalella azteca

Bioaccumulation and chronic toxicity of nickel (Ni) to Hyalella azteca in Ni-spiked sediments was strongly affected by the source of sediment used. The total range in LC50s on a sediment concentration basis ranged over 20 fold. Differences in Ni toxicity generally matched differences in Ni bioaccumulation, and toxicity expressed on a body concentration basis varied less than three fold. Body concentrations, therefore, provide a much more reliable prediction of Ni toxicity in sediments than do concentrations in the sediment. Ni in overlying water was also a reliable predictor of Ni toxicity, but only in tests conducted in Imhoff settling cones with large (67:1) water to sediment ratios. Overlying water LC50s for tests in beakers varied 18 fold. Sediment and body concentrations of Ni tolerated by Hyalella were slightly higher in cones than in beakers. Reproduction was not affected significantly by Ni at concentrations below the LC50 and 10-week EC50s for survival and biomass production (including survival, growth and reproduction) were only marginally lower than 4-week EC50s (survival and growth only).     

Lac Dufault sediment core trace metal distribution, bioavailability and toxicity to Hyalella azteca

To determine changes in metal distribution, bioavailability and toxicity with sediment depth, two 20-cm-long replicate cores were collected from a lake historically subjected to the influence of metal mining and smelting activity. The vertical distribution of Pb, Cd and Cu in sediment was similar for all three metals, with the surface layers showing enrichment and the deeper (pre-industrial) layers showing lower concentrations. Toxicity of each sediment core section was determined in laboratory tests with the freshwater amphipod Hyalella azteca. Bioavailable metal in each sediment slice was estimated from metal concentrations in overlying water in these toxicity tests and, for Cd, also from metal bioaccumulation. The profile for Cd in tissue was comparable to Cd in sediment and overlying water, but relative Cd bioavailability from sediment increased with sediment depth. Survival increased with increasing sediment depth, suggesting that surface sediments were probably less or non-toxic before industrialization.     

Exposure of Chironomus riparius larvae to uranium: effects on survival, development time, growth, and mouthpart deformities

Among non-biologically essential metals, data concerning uranium effects on freshwater benthic macroinvertebrates are scarce. The effects of uranium on survival, development time, growth and mouthpart deformities of midge Chironomus riparius were investigated. A 10-day static laboratory bioassay was performed exposing first instar larvae to artificial sediment spiked with four concentrations of uranium (2.97; 6.07; 11.44; 23.84 microg U g(-1) dry wt). As uranium was released from the sediment to the overlying water during this bioassay, both the sediment and the water column act as contamination pathways in giving rise to the observed effects. Significant negative effects on survival, development time, and growth were detected at 6.07, 6.07 and 2.97 microg U g(-1) dry wt, respectively. An LC20 of 2.49 microg U g(-1) dry wt (95% CI=1.48-4.27), and an LC50 of 5.30 microg U g(-1) dry wt (95% CI=3.94-7.25) were estimated. With respect to effects of uranium on larvae mouthpart deformities, we found that the lower the concentrations, the higher the deformity rates. These results highlight the potential impact of uranium at population level in environmentally realistic concentrations.     

Effects of low dissolved oxygen on organisms used in freshwater sediment toxicity tests

Minimum dissolved oxygen requirements are part of standard guidelines for toxicity testing of freshwater sediments with several benthic invertebrates, but the data underlying these requirements are somewhat sparse. We exposed three common test organisms to ranges of dissolved oxygen concentrations to determine their responses in 10-d exposures, relative to published guidelines for sediment toxicity tests. The oligochaete, Lumbriculus variegatus, showed 100% survival in all exposures down to the lowest concentration tested, 0.7 mg O(2)l(-1). Midge (Chironomus dilutus) larva showed a more pronounced response; while survival was less than 90% only below 1.0mg O(2)l(-1), the biomass endpoint showed EC(50), EC(20), and EC(10) values of 1.00 (0.91-1.10), 1.41 (1.16-1.71), and 1.67 (1.25-2.24) mg O(2)l(-1). The amphipod, Hyalella azteca, showed no adverse effects at concentrations as low as 2.12 mg O(2)l(-1). The combination of these data with other literature data suggest that DO minima in current North American 10-d sediment test guidelines are reasonable.     

The toxicity and bioavailability of atrazine and molinate to Chironomus tepperi larvae in laboratory and river water in the presence and absence of sediment

Acute (10 day) semi-static toxicity tests in which the midge, Chironomus tepperi, were exposed to atrazine and molinate were conducted in laboratory water and in river water, in the absence and presence of sediment. The bioavailability measured as median lethal concentrations (LC50) and 95% fiducial limits (FLs) of atrazine to C. tepperi in laboratory water in the absence and presence of sediment were 16.6 (14.3-19.4) and 21.0 (18.2-24.1) mg l(-1), respectively while the corresponding values in river water were 16.7 (14.7-19.0) and 22.7 (20.3-25.4) mg l(-1), respectively. For molinate, the LC50 and FL values in laboratory water in the absence and presence of sediment were 8.8 (6.8-11.4) and 14.3 (12.4-16.4) mg l(-1), respectively and the corresponding values in river water were 9.3 (7.6-11.3) and 14.5 (12.4-16.9) mg l(-1), respectively. Atrazine has low toxicity (LC50 > 10 mg l(-1)) while molinate has moderate toxicity (1 mg l(-1) < LC50 < 10 mg l(-1)) to C. tepperi. River water did not significantly (P > 0.05) reduce the bioavailability of either chemical to C. tepperi. However, the presence of sediment did significantly (P < 0.05) reduce the bioavailability of both atrazine and molinate to C. tepperi.     

Urinary concentrations of trichlorophenols in the Korean adult population: results of the National Human Biomonitoring Survey 2009

Trichlorophenols such as 2,4,5-trichlorophenol (2,4,5-TCP) and 2,4,6-trichlorophenol (2,4,6-TCP) are organochlorine compounds to which the general public can be exposed via contaminated food, water, and air. This study assessed exposure to 2,4,5-TCP and 2,4,6-TCP in Koreans age 18–69 years based on the Korean National Human Biomonitoring Survey conducted in 2009. Using data from 1,865 representative Koreans, we found that the geometric mean urinary concentrations of 2,4,5-TCP and 2,4,6-TCP were 83.4 pg/mL [95 % confidence interval (CI)?=?78.6–88.6] and 0.39 ng/mL (95 % CI?=?0.35–0.42), respectively. The creatinine-adjusted geometric mean 2,4,5-TCP and 2,4,6-TCP levels were 78.8 ng/g creatinine (95 % CI?=?73.8–84.1) and 0.36 μg/g creatinine (95 % CI?=?0.33–0.40), respectively. Of the Korean adult population, about 67.5 and 87.5 % had respective urine 2,4,5-TCP and 2,4,6-TCP concentrations >0.05 ng/mL (the limit of detection, LOD). Urine 2,4,5-TCP concentrations were significantly associated with age and place of residence, whereas urine 2,4,6-TCP concentrations were higher in rural residents. These findings suggest that most Koreans had detectable levels of 2,4,5-TCP and 2,4,6-TCP in their urine and that the body burden of 2,4,5-TCP and 2,4,6-TCP varied according to demographic and geographic factors.     

Toxicity of the mosquito control pesticide Scourge to adult and larval grass shrimp (Palaemonetes pugio)

This study investigated the toxicity of various concentrations of technical resmethrin and Scourge on adult and larval Palaemonetes pugio, a common grass shrimp species. Two types of tests were conducted for each of the resmethrin formulations using adult and larval grass shrimp life stages, a 96-h static renewal aqueous test without sediment, and a 24-h static nonrenewal aqueous test with sediment. For resmethrin, the 96-h aqueous LC50 value for adult shrimp was 0.53 microg/L (95% confidence interval (CI): 0.46-0.60 microg/L), and for larval shrimp was 0.35 microg/L (95% CI: 0.28-0.42 microg/L). In the presence of sediment, technical resmethrin produced a 24-h LC50 value for adult shrimp of 5.44 microg/L (95% CI: 4.52-6.55 microg/L), and for larval shrimp of 2.15 microg/L (95% CI: 1.35-3.43 microg/L). For Scourge, the 96-h aqueous LC50 for adult shrimp was 2.08 microg/L (95% CI: 1.70-2.54 microg/L), and for larval shrimp was 0.36 microg/L (95% CI: 0.24-0.55 microg/L). The 24-h sediment test yielded an LC50 value of 16.12 microg/L (95% CI: 14.79-17.57 microg/L) for adult shrimp, and 14.16 microg/L (95% CI: 12.21-16.43 microg/L) for larvae. Adjusted LC50 values to reflect the 18% resmethrin concentration in Scourge are 0.37 microg/L (adult), 0.07 microg/L (larvae) for the 96-h aqueous test, and 2.90 microg/L (adult), 2.6 microg/L (larvae) for the 24-h sediment test. Larval grass shrimp were more sensitive to technical resmethrin and Scourge than the adult life stage. The results also demonstrate that synergized resmethrin is more toxic to P. pugio than the nonsynergized form, and that the presence of sediment decreases the toxicity of both resmethrin and Scourge.     

Concentrations of pentachlorophenol (PCP) in fish and shrimp in Jiangsu Province, China

Pentachlorophenol (PCP) concentrations were determined in 55 samples of fish, shrimp, crabs, frogs and turtles collected in Jiangsu Province and 55 freshwater shrimp samples collected from the Huiming Fish Market, Nanjing, China between 2003 and 2004. PCP concentrations ranged from less than the method detection limit (MDL: 0.5 microg/kg ww) to 61 microg/kg ww, with a mean of 5.2 microg/kg ww in 55 samples collected across Jiangsu Province and a mean of 0.5 microg/kg ww for freshwater shrimp collected from the Huiming Fish Market. Concentrations of PCP in common carp (Carassius auratus) were significantly greater than concentrations of PCP in other species from all of the areas studied. Grass carp (Ctenopharyngodon idella) contained the second greatest concentrations and crustacean species contained the least concentrations. Concentrations of PCP were greater in samples collected from Southern Jiangsu than those collected from other areas of Jiangsu Province. Concentrations of PCP in the freshwater shrimp (Macrobrachium nipponense) from the Huiming Fish Market were greater in March and September than those collected in June and December. Based on the allowable daily intake (ADI) set by the US National Academy of Science, current concentrations of PCP measured in aquatic products from Jiangsu Province presented minimus health risks to humans.     

PCDD/DF formations by the heterogeneous thermal reactions of phenols and their TiO2 photocatalytic degradation by batch-recycle system

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/DFs) formation by the thermal reactions of phenols with CuCl2 under oxygen flux were carried out in relation to their formation mechanisms. To evaluate the effect of photocatalytic degradation of titanium dioxide (TiO2) thin film prepared by the sol-gel method, the photocatalysis of PCDD/DFs in acetonitrile/water solution by batch-recycle system was conducted. For the thermal reaction system of powder mixtures of 2,4,5-trichlorophenol (2,4,5-TCP) and CuCl2, the formation rates were 8.1 microg/g-2,4,5-TCP/min for total PCDD/DFs and 6.9 microg/g-2,4,5-TCP/min for PCDDs, and total PCDD/DF rate was higher by approximately 40 fold compared to phenol vapor/oxygen/CuCl2 powder system. For the system of 2,4,5-TCP, PCDDs were mainly formed via ortho-phenoxyphenols (POP) intermediate by the condensation of 2,4,5-trichlorophenate. For PCDD/DF photocatalytic degradations, most PCDD congeners photodecomposed rapidly and the rates presented more than 70% (as dechlorination rates of 76% for PCDDs) at 24 h after irradiation, using PCDD/DFs formed with 2,4,5-TCP. The rate constants were in the order of 4.8-6.1 x 10(-3) min(-1), assuming the pseudo-first-order reactions for their low levels.     

Environmental fate and bioavailability of wood preservatives in freshwater sediments near an old sawmill site.

Impacts of an old contaminated sawmill site located in Eastern Finland were studied, with emphasis on transportation and bioaccumulation of wood preservatives in the surrounding water system. To assess the transportation of chlorophenols and chromated copper arsenate (CCA) from the sawmill to the nearby lake, the concentrations of these compounds in selected sediment samples were analyzed. To assess the contribution of a pulp mill further upstream, the concentration of extractable organic halogens (EOX) was analyzed. Bioaccumulation of wood preservatives from sediments was examined using Lumbriculus variegatus as test organism. In sediments collected from the sawmill area, concentrations of chlorophenols, arsenic, chromium and copper were high. In the surrounding area the concentrations of these compounds were slightly elevated at some sampling points but were mostly within the natural range of variation. Thus, it can be concluded that transportation of wood preservatives from the sawmill area to its surroundings is fairly low. However, 60 microg/l of arsenic and 50 microg/l of copper were found in water taken from a brook that runs through a landfill area of the sawmill to the nearby river, and the concentration of arsenic in the surface sediment at one sampling point in the lake was slightly elevated. The total amount of organohalogens in sediment was higher in the river and the lake than in the sawmill area. Of all the wood preservatives studied, only arsenic was found to bioaccumulate in present conditions, reaching a tissue concentration of 362 microg/g dw in organisms exposed for 28 days to sediment from the brook. High concentration of arsenic in oligochaeta tissue was related to high concentration of arsenic in the pore water.     

Studies on lethal concentrations and toxicity stress of some xenobiotics on aquatic organisms

Three widely used xenobiotics pentachlorophenol (PCP), 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-chloro-2,6-diethyl-N-(butoxymethyl) acetanilide (Butachlor) are evaluated for acute toxicity and stress behavior on freshwater fish (Heteropneustes fossilis, Clarias batrachus, Channa punctatus) and mosquito larvae (Culex pipiens fatigans). The experiment was carried out by medium treatment using intermittent flow-through system. Median lethal concentrations (LC50) were calculated by probit analysis. The LC50 values and 95% confidence intervals showed variable range for tested chemicals. Mosquito larvae generally appeared resistant than fish, while H. fossilis was found to be most sensitive. Stress signs in the form of behavioral changes are also observed. Both types of organisms are recommended as good bioindicator for the risk assessment of aquatic environment due to chemicals tested.     

Interactions between a polycyclic aromatic hydrocarbon mixture and the microbial communities in a natural freshwater sediment

The toxicity of a polycyclic aromatic hydrocarbon (PAH) mixture was assessed on the indigenous microbial communities of a natural freshwater sediment. The fate and effects of the PAH mixture (phenanthrene, fluoranthene and benzo(k)fluoranthene) were studied over 28 days. Bacterial communities were described by bacterial counts (total bacteria and viable bacteria), and by some hydrolytic enzyme activities (beta-glucosidase and leucine-aminopeptidase), PAH concentrations were measured in the overlying waters and in the sediments. No effect of PAH was detected at 30 mg/kg for all bacterial parameters. At 300 mg/kg, the quantity of total bacteria and the proportion of viable bacteria markedly decreased, compared to the control (0 mg PAH/kg). At 300 mg/kg, an increase of the beta-glucosidase activity and a decrease of the leucine-aminopeptidase activity were observed. For all treatments, the benzo(k)fluoranthene concentration in the sediment was stable over 28 days whereas, in the same time, only 3-6% of the initial concentrations of phenanthrene and fluoranthene remained. This study shows that (1) PAH induce perturbations of sediment microbial communities in terms of density and metabolism (but not always as an inhibition), (2) indigenous bacteria of sediments might be used for toxicity assessment of specific organic pollutants, (3) native microorganisms of sediment seem to have a high capacity for PAH degradation, depending on the physico-chemical properties and the bioavailability of the substance encountered.     

2,4-Dichlorophenoxyacetic acid (2,4-D) biodegradation in river sediments of Northeast-Scotland and its effect on the microbial communities (PLFA and DGGE)

A bench-scale study was conducted to investigate 2,4-D biodegradation rates at different concentrations (10, 100 and 1000 microg per gram of dry weight) in distinct sediments samples collected on the River Ythan, Northeast-Scotland. Mineralisation of 14C 2,4-D occurred mostly within 30 days for all tested concentrations with a degradation rate ranging from 5 to 750 microg d(-1). Biodegradation rates were affected by the biological and biochemical characteristics of the indigenous microbial community in the studied sediments rather than factors such as compound bioavailability and/or toxicity. PLFA-profiling provided evidences of the effect of 2,4-D amendments on the microbial communities and DGGE-profiling showed changes in the genetic potential of the microbial populations which might affect metabolic characteristics of the sediment. PLFAs biomarkers suggested that the pathway of alpha-ketoglutarate-dependent dioxygenase was the main route of 2,4-D biodegradation. This pathway is commonly found in microorganisms of the beta-subdivision of proteobacteria.     

Endocrine modulation and toxic effects of two commonly used UV screens on the aquatic invertebrates Potamopyrgus antipodarum and Lumbriculus variegatus

The two UV screens 3-benzylidene-camphor (3-BC) and 3-(4'-methylbenzylidene)-camphor (4-MBC) were tested regarding their toxicity and estrogenic activity. The Yeast Estrogen Screen (YES) and two sediment assays with the freshwater invertebrates Lumbriculus variegatus and Potamopyrgus antipodarum were performed. In the YES, both substances activated the human estrogen receptor alpha with EC50 values of 44.2 microM for 3-BC and 44.3 microM for 4-MBC, whereby 4-MBC attained only 8% of the maximal response of 17beta-estradiol. For P. antipodarum embryo production increased after exposure to both substances (EC50 of 4.60 microM 4-MBC=1.17 mg kg(-1)dw) while mortality increased at high concentrations. The reproduction of L. variegatus was decreased by 3-BC with an EC50 of 5.95 microM (=1.43 mg kg(-1)dw) and also by 4-MBC, where no EC50 could be calculated. While reproduction decreased, the worms' weight increased after exposure to 3-BC with an EC50 of 26.9 microM (=6.46 mg kg(-1) dw), hence the total biomass remained unaffected.     

Water quality and fish size affect toxicity of endosulfan, an organochlorine pesticide, to rainbow trout

The acute toxicity of endosulfan in juvenile rainbow trout (Oncorhynchus mykiss, 10.61+/-1.69 g) was evaluated in glass aquaria under static conditions. Nominal concentrations of endosulfan in the toxicity test ranged from 1.3 microg l(-1) to 29 microg l(-1). The concentrations of endosulfan that killed 50% of the rainbow trout within 24-h (24-h LC50), 48-h LC50, 72-h LC50, and 96-h LC50 were 19.78, 8.89, 5.28, and 1.75 microg l(-1), respectively. None of the unexposed control fish died, and the first fish died 4 h after exposure to 26.3 microg l(-1) of endosulfan. Survival of fish was significantly increased with increasing fish size and decreased with decreased fish size at the same temperature (p<0.001). Temperature also had a significant effect on survival of fish. Alkalinity at levels above 20 mg l(-1) as CaCO3 significantly increased survival of fish at 19.78 microg l(-1) of endosulfan. Increasing alkalinity from 20 mg l(-1) as CaCO3 to 42 or higher concentrations tested in this study (121 mg l(-1) as CaCO3) significantly increased survival of fish (p<0.01). Total hardness ranging from 55 mg l(-1) as CaCO3 to 126 mg l(-1) as CaCO3 did not affect survival of fish exposed to endosulfan. Endosulfan toxicity was found to be irreversible when fish were exposed to minimum concentrations of endosulfan tested. Histologically, fish gills had lamellar edema, separation of epithelium from lamellae, lamellar fusion, and swelling of the epithelial cells. Melanomacrophage centers were scattered throughout the trunk kidney, head kidney, and spleen. The liver of endosulfan-exposed fish had severe focal necrosis. None of these lesions were seen in unexposed control fish. Results indicate that alkalinity, temperature, and fish size affect endosulfan toxicity of rainbow trout.     

Spatial distribution of acid-volatile sulphide concentration and metal bioavailability in mangrove sediments from the Brisbane River, Australia

Acid-volatile sulphide (AVS) was measured at regular positions along eight transects through a mangrove forest in the Brisbane River, Queensland, Australia. Concentrations ranged from 0.33 to 22.61 micromol S g(-1) sediment dry weight. There was no correlation between AVS concentration and the proportion of clay-sand in the sediment, but sediments with high AVS concentrations tended to contain more water (rs=0.43; p=0.01). AVS concentrations were used to assess the potential bioavailability of the sediment heavy metal burden. The spatial variability of potential bioavailability was high and depended to a great extent on which metals were considered as part of the AVS complexing system. It is suggested seasonal variations would further increase the observed variability in bioavailability. This variation should be taken into account when monitoring and assessing long-term trends in sediment toxicity.     

Bioavailability of PCBs from field-collected sediments: application of Tenax extraction and matrix-SPME techniques

Two chemical approaches, Tenax extraction and matrix solid phase microextraction (matrix-SPME), were evaluated for their potential to improve the prediction of bioavailability by equilibrium partitioning theory (EPT) across sediments with various characteristics. Biota-sediment accumulation factors (BSAFs) and body residues were quantified by exposing Lumbriculus variegatus to three PCB-contaminated field sediments. The concentration of PCBs in biota was positively correlated to the total PCB sediment concentration, the PCB concentration in the rapidly desorbing fraction estimated using Tenax extraction, and the PCB concentration on the SPME fibers. Results showed EPT was acceptable for estimating bioavailability from the tested sediments with sum PCB BSAFs of 1.18-2.47; however, it overestimated PCB bioavailability from sandy sediment. Both Tenax extraction and matrix-SPME, which take sequestration into account, reduced variability in prediction of PCB bioavailability across sediments, including the sandy sediment, and could be used as cost- and time-efficient alternatives for bioassay. Matrix-SPME was considered the better technique due to its ability to directly predict PCB body residues in the exposed biota and its potential use with in situ applications in the field.     

Pyrene bioavailability; effect of sediment-chemical contact time on routes of uptake in an oligochaete worm

Bioavailability of sediment-sorbed compounds may vary with increasing contact time. This may result in the dietary uptake route becoming more significant as conditions in the gut flora aid the extraction of contaminants, which have migrated into sites within the sediment particle. Such mechanisms may have important implications on risk assessments performed on substances released into the environment. A series of experiments were carried out using sediment spiked with 14C-labelled pyrene, a polycyclic aromatic hydrocarbon. The sediment was left at room temperature over a period of 220 days. Periodically (at 0, 1, 14, 28, 70, 220 days) the sediment was used to perform a bioaccumulation study using the freshwater oligochaete Lumbriculus variegatus. A novel methodology using feeding and (decapitated) non-feeding worms, allowed differentiation between uptake via ingestion and simple sorption. Results showed that there was a decline in bioavailability with time and that this was a 3 stage process. A rapid initial decline was observed over the first day when a 40% decrease was measured, an intermediate period were levels remained stable (day 14 to day 70) and an ultimate decrease in pyrene activity in worm tissue of 70% after 220 days. Over this period the chemical extractability of pyrene also decreased by 50%, as the chemical migrated deeper into unavailable sites within the sediment matrix. Normalising bioavailability to the chemically extractable fraction of pyrene within the sediment provided an overall decrease in bioavailability of 58%. The importance of the dietary route of uptake for pyrene varied during the sediment aging process, reflecting the changes in the physico-chemical interactions between the pyrene, sediment and pore water.     

Evaluating the role of desorption in bioavailability of sediment-associated contaminants using oligochaetes, semipermeable membrane devices and Tenax extraction

The success of the rapidly desorbing fraction as an available fraction was challenged by using sediment ingesting and non-ingesting oligochaetes (Lumbriculus variegatus) together with passive samplers (semipermeable membrane devices, SPMDs) in accumulation and kinetic modelling exercises for carbon-14 labelled model compounds (pyrene, benzo[a]pyrene and 3,4,3',4'-tetrachlorobiphenyl). Passive samplers clearly produced lower uptake rate constants and steady state factors than either of the oligochaete treatments when residue concentrations were based on animal lipid or total SPMD weight. The rapidly desorbing chemical fractions in sediments did not show a significant relationship with the biota sediment accumulation factors or SPMD accumulation factors. A distinctly better relationship was observed between the accumulation factors and the desorption rate constants. The results support the assumption that desorption plays an important role in bioavailability, although animal behaviour and the diffusional limitations of hydrophobic contaminants in sediment together probably affect the actual available pool.